According to the prosecution representing Morrisons at the Bradford Crown Court trial, 43 year-old Andrew Skelton decided to publish the database containing employee names, addresses, bank account numbers and national insurance numbers, in revenge for being incorrectly disciplined for receiving packages at the company’s head office in Bradford.

Image: Morrisons

Morrisons initially believed that one package contained drugs but it transpired that Skelton was using the mailroom for to buy and sell goods on eBay.

The firm said it believed that this lay at the root of his decision to leak data that had it fallen into the wrong hands would have constituted one of the most serious data breaches in British corporate history.

Skelton also write a resignation letter in the days before the incident in March 2014. “I have almost as little concern for the company as it does for me,” he is alleged to have written.

A study in 2010 found that worries over data breaches from employees was exaggerated although when incidents did occur they tended to be noteworthy. In the past, incidents often focussed on network sabotage rather than data theft.

The Morrisons case does beg some questions about the company’s security policies. Skelton worked as an IT auditor and so had access to the sensitive data but how was he able to steal the entire employee database without this being detected? As the case progresses, more detail of how he bypassed security may be revealed.

The prosecution has also claimed that the disciplinary incident lay at the root of Skelton's alleged actions but has so far not explained why he would have carried out such a hugely damaging act for a relatively reprimand that had been withdrawn.

Morrisons claims that investigating and remediating the theft cost it £2 million ($3.1 million).

"With Morrisons' estimated £2 million bill to fix this data breach, this particular clean-up will be significantly more expensive than a spillage in aisle four,” commented EMEA sales vice president for cloud security firm Netskope, Eduard Meelhuysen.

"These findings show that companies must monitor apps in use by employees and coach them towards approved solutions, as well as setting policy to prevent the upload of sensitive information which could result in a costly data breach."